title: The molecular basis of allorecognition in ascidians.
abstract: The process of allorecognition consists of an ability to discriminate self from non-self. This discrimination is used either to identify non-self cells and reject them ("non-self histocompatibility") or to identify self cells and reject them (as in the avoidance of self-fertilization by hermaphrodites ("self incompatibility"). The molecular basis governing these two distinct systems has been studied recently in hermaphroditic ascidian urochordates. Harada et al. postulated two highly polymorphic self-incompatibility loci, Themis (A and B), that are transcribed from both strands, forward to yield sperm (s-) trans-membrane antigen, and reverse to yield the egg vitelline coat (v-) receptor. De Tomaso et al. characterized a candidate histocompatibility locus, encoding a highly variable immunoglobulin. Nyholm et al. isolated its candidate allorecognition receptor, fester. Only a minute similarity was found in the structure of the genes involved. It appears that ascidian harbor two very separate types of labeling and recognition genetic systems: one for self and the other for non-self.
authors.affiliation: Department of Biology, Faculty of Science and Science Education, University of Haifa-Oranim, Tivon 36006, Israel. ekly@research.haifa.ac.il
authors.forename: Rachel
authors.initials: R
authors.lastname: Ben-Shlomo
mesh_terms: D000818:Animals; D005260:Female; D005306:Fertilization / Q000276:immunology; D014644:Genetic Variation; D006649:Histocompatibility Antigens / Q000737:chemistry; D007107:Immune System; D007136:Immunoglobulins / Q000737:chemistry; D008285:Major Histocompatibility Complex; D008297:Male; D008954:Models, Biological; D010063:Ovum / Q000378:metabolism; D013084:Sperm-Ovum Interactions / Q000235:genetics / Q000276:immunology; D013094:Spermatozoa / Q000378:metabolism; D014561:Urochordata / Q000378:metabolism / Q000502:physiology*; D014817:Vitelline Membrane / Q000276:immunology
chemical_list: D006649:Histocompatibility Antigens; D007136:Immunoglobulins